Preheat your Yoder Smokers YS640s Pellet Grill to 450°F, set up for direct grilling, with the door in the diffuser removed (or entire diffuser).
Combine the Sweetwater Spice Ancho Chipotle Brine Concentrate and water in a Briner Mini 4 quart Briner Bucket. Whisk well. Add the chicken thighs. Marinate thighs for 45-60 min.
To make the salsa verde, grill peppers, tomatillos and onion over direct flame until the onion and tomatillos are lightly charred and softened, then remove. Char the peppers on all surfaces, then remove from grill and transfer to a zip top bag.
Allow the peppers about 10 minutes to steam in the bag. Meanwhile, dice on the onion and place in a blender pitcher with the tomatillos, cilantro and garlic.
Remove the peppers from the bag. Peel off the skins and remove the seeds. Dice the flesh and add to the blender. Blend until smooth. Season with salt, to taste.
Remove the chicken thighs from the Briner Bucket. Pat excess marinade off the surface with a towel. Season the chicken with Cattleman’s Grill Mexicano Seasoning.
Grill the thighs over direct heat until the internal temperature reaches 175°F, flipping to brown both sides. Remove from grill and shred meat.
Lower the heat in the grill to 400°F, and place the door back in the diffuser (or return the entire diffuser to the grill) to set up for indirect grilling. Place the second shelf in place in the grill, as well.
To make the sour cream sauce, melt the butter in a Lodge 8” Cast Iron skillet over medium heat. Add the flour and whisk to make a roux. Keep the roux moving until it just becomes aromatic, about 1 minutes. Add the stock, slowly at first, whisking constantly until all stock is incorporated. Bring to a simmer. Whisk in sour cream and pepper jack cheese. Cook until thickened, just a few minutes.
Combine shredded chicken and sour cream sauce. Mix well.
Roll 1/4 cup of the chicken into each tortilla.
Pour 1/2 cup salsa verde in a half sized foil pan. Spread to cover the bottom of the pan. Place the rolled enchiladas in the pan. Pour the remaining salsa verde and pepper jack cheese over the top.
Place the pan full of enchiladas on the second shelf of the grill and bake until the cheese on top is melted and browning and the sauce is bubbling around the edges, about 45 minutes.
Remove from the grill and serve warm.